Disposable centrifuge bowls have been developed for processing anticoagulated whole blood in pheresis, deglycerolization and cell washing procedures. Prior to about 1986, commercially available disposable blood processing centrifuge bowls were of the type generally shown in FIGS. 1 or 6 of U.S. Pat. No. 4,300,717 (hereinafter "Latham bowl"), or U.S. Pat. No. 4,086,924 (hereinafter "Grenade-type bowl"), [each of which is incorporated herein in their entirety by reference]. The overall bowl construction in each case was similar and consisted of three essential units. The first unit is a multi-piece feed tube and seal assembly, which enables fluids, such as, anticoagulated whole blood and/or wash solution, to be introduced from a fixed location to the interior of a rotating bowl body and processed blood component to be removed from the bowl body and returned to a patient or donor, or stored.
The second unit is comprised of a two-piece bowl body welded together at a peripheral seam.
The third unit is a core usually of fairly solid construction. The core serves a number of functions. In the Latham bowl, the core provides a narrow bottom fluid channel between the base of the core and the bottom of the bowl, through which fluid, admitted through a central feed tube, is passed to the outer periphery of the bowl body interior. In passing through this narrow channel, "impeller" vanes, formed on the bottom of the bowl, imparted rotational velocity to the incoming feed fluid. With the core design shown in the Latham bowl, fluid feed is forced to pass to the outer separation region between the inner peripheral bowl body wall and the outer peripheral wall of the core. From the outer wall, the fluid then must flow inside to reach the effluent port. Without this core design, it would be possible for fluid admitted at the bottom of the bowl to by-pass the processing region and pass directly from the feed tube upwardly through the space between the inner core wall and the feed tube out the effluent port formed between the skirts of the seal assembly. The rigid core body was considered essential to avoid or dampen fluid wave vibrations which might occur between the rotating sterile air in the central region between the core and the feed tube and the fluid processed in the outer separation region.
The Grenade bowl construction is similar, except that the middle bowl body side walls are not tapered and the bottom of the core is not flared. Also, the core of the Grenade-type bowl does not force input feed fluid out to the periphery. Thus, fluid flows from the inside-out in the processing region.
Sometime during 1986/87, a new centrifuge bowl became commercially available. The construction of this bowl is shown in the FIGS. 4-6 embodiment of U.S. Pat. No. 4,983,158 (hereinafter the "Headley bowl" and incorporated herein in its entirety by reference). This new bowl differed from the prior art bowl by the use of a one-piece integral blow molded bowl body.
The FIGS. 4-6 embodiment of the Headley bowl utilized a one-piece core body with an outer diameter equal to or smaller than the opening into the bowl. The small core size, as in the Grenade-type bowl, is insufficient to enable the core to force feed fluid, entering the bottom of the bowl through the feed tube, to be diverted to the extreme outer periphery of the processing region between the core body and the bowl wall. This diversion is important for cell washing applications.
In cell washing systems, shed blood from a patient is filtered, collected and washed with saline in a disposable centrifuge bowl. Anticoagulated, filtered shed whole blood enters at the bottom center of the bowl and is separated by centrifugal forces into more dense red cells and less dense other components. The red cells fill the outermost portion of the rotating centrifuge bowl. As more shed blood enters the bowl, the red cells remain in the bowl displacing the supernatant (saline, plasma, contaminants, etc.) out of the mid-central region of the bowl. This concentrates the red blood cells in the bowl. Next, saline is directed into the bottom of the bowl, instead of shed blood. Saline, entering the Latham bowl, is directed by the lower extended skirt portion of the core to the outermost radius of the bowl and through the bed of packed red blood cells. In this way, the supernatant is diluted and displaced by the saline until a satisfactory amount of non-red blood cell fluid, i.e., plasma, anticoagulant and contaminants, originally entering the bowl, are removed by the wash process. The centrifugal washing procedure in conjunction with filtration concentrates the red blood cells and removes contaminants, such as blood clots, bone chips, fatty tissue and activated clotting factors. The patient can then be reinfused with his or her own washed red blood cells.
The referenced Headley bowl lacks a diverter structure, as in the Latham-type bowl. Therefore, some of the saline wash solution may not be forced to travel to the extreme outer periphery before exiting the bowl through the effluent skirts on the rotary seal. This substantially decreases the cell washout efficiency and, hence, the time it takes to complete a cell washing procedure.
In the FIG. 7 and FIGS. 9-10 embodiments of the Headley bowl and in the bowl of U.S. Pat. No. 4,943,273 (hereinafter the "Pages bowl"), [and incorporated herein in its entirety by reference], core structures are disclosed which permit use of an integral bowl body, while providing a diverter structure.
In one embodiment, the core is formed of one-piece construction using semi-rigid plastic material with a flared core and a wall body which can be deflected to allow the flared core to be inserted through the smaller diameter opening (FIG. 7 of the Headley bowl patent).
In another embodiment, the core is of two-piece construction. One piece is comprised of a generally cylindrical hollow walled core. The other piece is a disc-like member with a flared wall portion adapted to be located adjacent the diagonal wall of the bowl body (FIGS. 9-10 of the Headley bowl patent).
In the embodiment of the Pages bowl patent, the core assembly consists of two plastic pieces made by injection molding or similar processes. The first piece is a generally cylindrical rigid hollow-walled core, similar to the walled core in the parent application. The second piece is a diverter in the form of a semi-rigid donut-like member, scalloped at its peripheral edges and having an outer diameter greater than the bowl opening and about equal to the inner diameter of the mid-section of the bowl.
An inner hole is provided on the donut-like member. This hole has a diameter slightly smaller than the diameter of the skirt of the effluent tube.